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question about grounding


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Hi all,

I inspected a 100+ year old home this morning with an overhead service that had the grounding conductor that comes out of the meter disconnected from the ground rod. The rod was nowhere in sight (maybe properly buried, maybe not there at all) but the grounding wire was hanging down with the acorn clamp still attached.

All the "grounded" outlets tested correctly using a three prong tester. The plumbing was not bonded (the main water supply was plastic tubing) and there was no visible grounding wire coming from the Pushmatic electric panel. My question is why do the outlets show that they are grounded? Where should I be looking to find where the system is grounded. Or do I need to upgrade to a new way of testing? (I don't know if it makes any difference but the home is aluminum sided)

As always, all assistance is greatly appreciated. Thanks

The picture is hard to see but behind the downspout is the wad of grounding conductor

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Grounding of the service has nothing to do with grounding of receptacles. The receptacles are "grounded" by connecting them to the grounded conductor at the service. They will be "grounded" even if a ground rod or water line is not connected to the service.

Don't worry, it only takes about 10 years to understand these concepts.

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I would definitely write it up as "the service equipment is not grounded to current standards." A primary issue is... what will happen in the event of a lightning strike?

You did not mention what type of wiring system. Sorry the pic didn't post. Are there equipment grounding wires present at the circuits and are they run back to an equipment grounding terminal at the panel? Is it hard piped conduit where the conduit serves as the equipment grounding conductor? If they are tied to the neutral bar at the panel the system will appear as grounded which is where I think Mark was going with it. What do you see inside the panel? Does your tester identify bootleg or false grounds (the neutrals and equipment grounding conductors tied together at the outlets?) The Sure Test is the only one I am aware of that will identify this condition.

Doug Hanson's book Electrical Inspection of Existing Dwellings is a tremendous resource in understanding the vagaries of what most of us hold to be the most difficult to understand system in the house.

The Pushmatic panel is considered an obsolete piece of equipment in my neck of the woods. I would defer the entire system for further evaluation citing lack of equipment grounding and an obsolete electrical panel.

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What Mark & Crusty said. The grounding of receptacles is achieved by connecting them to the grounded (AKA "White" or "Neutral") service bus. The presence or absence of an earth ground has no effect on them.

However, as Crusty said, the missing earth ground *is* a problem and should be fixed but it has more to do with the action of outside influences on the system (lightning) than on the day-to-day functioning of the system.

I'd like to mention that, in my neck of the woods, Pushmatic panels are not necessarily obsolete. We have pushmatic installations that were installed new out of the box in 1992.

- Jim Katen, Oregon

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Originally posted by mcramer

Grounding of the service has nothing to do with grounding of receptacles. The receptacles are "grounded" by connecting them to the grounded conductor at the service. They will be "grounded" even if a ground rod or water line is not connected to the service.

Don't worry, it only takes about 10 years to understand these concepts.

I want to shorten the time from 10 years to something less. What you are describing as "grounding" is actually "bonding", no?

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Sorry about the pic, I guess it really WAS hard to see. Better luck next time.

>You did not mention what type of wiring system. Sorry the pic didn't post. Are there equipment grounding wires present at the circuits and are they run back to an equipment grounding terminal at the panel? Is it hard piped conduit where the conduit serves as the equipment grounding conductor? If they are tied to the neutral bar at the panel the system will appear as grounded which is where I think Mark was going with it. What do you see inside the panel? Does your tester identify bootleg or false grounds (the neutrals and equipment grounding conductors tied together at the outlets?) The Sure Test is the only one I am aware of that will identify this condition.

Doug Hanson's book Electrical Inspection of Existing Dwellings is a tremendous resource in understanding the vagaries of what most of us hold to be the most difficult to understand system in the house.<

As far as the panel goes, there is 12/2 and 14/2romex with grounds as well as flexible metal conduit, and that silvery sheathed wire going into it. Even two aluminum branch circuits that are corroding at the breaker connection. The neutrals and grounds are tied together at the panel as you mentioned.

>What Mark & Crusty said. The grounding of receptacles is achieved by connecting them to the grounded (AKA "White" or "Neutral") service bus. The presence or absence of an earth ground has no effect on them. <

Okay, I get it now.[:-bulb]

>If you are using a 3 Light Night Light tester then you need to upgrade to a SureTest.<

Time to upgrade once again.

I will also order the Hansen book pronto, I have seen it mentioned a few times before and now its importance has finally sunk in. It seems that every panel I see has a new mystery and every electrician I speak to has their own way of making sense of it. This forum has the means of distilling it all to what is important for the home inspector.

>I want to shorten the time from 10 years to something less.<

I'm with you, Kurt. Its great to read what you guys have to say and I feel privaleged to be able to ask questions.

This has been a big help in thinking about whats inside the box. thanks

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Even two aluminum branch circuits that are corroding at the breaker connection. The neutrals and grounds are tied together at the panel as you mentioned.

I would recommend further evaluation of that condition along with a recommendation to apply antioxident paste to prevent the corrossion which will result in brittleness and breakage.

I assume that you are talking about stranded, not solid, aluminum.

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Originally posted by crusty

Doug Hanson's book Electrical Inspection of Existing Dwellings is a tremendous resource in understanding the vagaries of what most of us hold to be the most difficult to understand system in the house.

Here here. An excellent book, one of my first-line electrical references.

Brian G.

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Hi Eric,

I think the spaces need to be taken out of the picture name. If you're using Mozilla or Netscape you have to go through the upload process and manually copy and paste the link it makes for the post.

We're all friendly here, but your client's name should probably not be in the pic title.

All that's out of the way..thanks for asking the question, I learned something today.

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